B - "Don’t marry the relative because the child will be cadaverous." (**)

I did not find words of the first narration in any compilation of Hadith except the book entitled “Gharib Al Hadith” by Al Harbi who commented to this narration by saying: “They (Al Arab) believed that if a person marries daughter of his uncle his progeny becomes small and weak but if she is strange the progeny comes stronger and taller. Therefore, it was said: (Marry a stranger and don't have a weak child) In other words: Marry the strangers and don’t have emaciated progeny or avoid having weak and thin offspring.” (1)

I found both narrations together in An-Nihayah, as the compiler mentioned the narration (Marry a stranger and don't have a weak child) then he commented on this Hadith and said: “And similar to this is the Hadith: (Do not marry close relatives ...) End of quote.

Al `Iraqi quoted Ibn Salah who said: "I did not find any sound basis for this narration." Then he added: "It is rather known of the sayings of `Umar, who told the family of Ass-Sa’ib: “You have become sickly, so marry non-relatives.” This was narrated by Ibrahim Al Harbi in Gharib Al Hadith, he explained it saying: “It means: marry non-relatives as it was said: (Marry afar and do not become sickly.)” (2) (End of quote).

Although, I did not find the reference in the published copy of Gharib Al Hadith, perhaps it is in the missing copy of this book. Al Hafiz Ibn Hajar mentioned the chain of this narration to Al Harbi and said: “Ibrahim Al Harbi narrated it in Gharib Al Hadith on the authority of `Abdullaah ibn Al Mu’ammal, from Ibn Abu Mulaykah who said: `Umar advised the family of Ass-Sa’ib ....." (3). End of quote.

`Abdullaah ibn Al Mu’ammal is Al Makhzumi was weak. (4)

Reasoning:

These texts (a) and (b) were held as evidence by many of physicians and writers including: Dr. Mahmud Nazim An-Nasimi in his book (Prophetic Medicine and Modern Science) (5), Dr. Muhammad `Ali Al Barr in his book (Is there a Prophetic medicine ), and (The concise about embryology) (6), Dr. Hamid Ahmad Hamid in his book (Journey of faith in the human body) (7), Al Hafiz Yusuf Musa in his book (Sex in Islam and secularism) (8), `Abdullah Naseh `Alwan in his book (Raising Children in Islam) (9), Muhammad Kamel `Abduss- Samad in his book (Scientific miracles in Islam – The Prophetic Sunnah) (10), and Dr. Samiyah Hasan Ass-Sa`a’ti in her book (Choosing for marriage and social change) (11).

The text of (a) was quoted by Dr. Khales Jalabi in his book (Medicine a dignified platform for the faith) (12), Dr. Muhammad `Ali Al Barr in his book (Work of woman on criteria ) (13), Dr. `Abdul Hamid Diyab and Dr. Ahmad Qurquz in their book (With medicine in the Qur'an) (14), Dr. `Izzudd-Din Farraj in his book (Islam and prevention from diseases) (15), Dr. `Umar Al Alfi (16). All of them conclude that both texts agree with the discovery of genetic science which confirms that consanguineous marriage leads to diseases and damages in progeny.

However, some of them shortened their words and concluded in brief that marriage between relatives leads to emaciation and weakness of offspring, while others elaborated this issue. Before quoting their words, I would like to remind that fetus is formed by integration of sperm that carries 23 chromosomes with the egg which carries the same number of chromosomes. These chromosomes carry a huge number of genetic traits. (17)

These traits are divided into: prevalent trait: (i.e., capable of appearing in the fetus) and recessive trait that is weak and can not appear alone on the fetus until both of them come together, such as the weak Hadith is strengthened by another one.

Dr. Al Barr said: "As the genetic traits may be dominant or may be recessive, the recessive characteristics will not be manifested neither in father nor mother but if it happened that father and mother both were carrying one of these recessive characteristics then this recessive characteristic will appear obviously and clearly in about a quarter of their children, due to the presence of the two characters in both.

This is what makes marriage between relatives (Consanguinity), promote the hidden recessive characteristics and disease to appear, since both father and mother having close kinship carry a lot of common and recessive characteristics which do not appear in them but when they are united by marriage the possibility of the emergence of these recessive traits becomes very large.

For example, some genetic diseases that are rare in community the probability of their appearance in the couples having far kinship does not rise to one per thousand, while the possibility of emergence of that rare hereditary disease rises to 35%, if the couples are cousins.

The recessive hereditary diseases are too many, including disease of imbalance in the metabolism (Inborn Error of Metabolism), Wilsons Disease, Taysacs , Albinism and black urine disease (Alcaptonuria), even the number is more than a hundred disease known to the specialist physicians.